Pre-selection of sex has been accomplished in many species of livestock following the development of safe and reliable methods of separating sperm cells into enriched X chromosome bearing and Y chromosome bearing populations. See for example methods and apparatus disclosed by WO 00/06193; WO 02/043574; WO 01/85913; WO 99/33956; WO 01/40765; WO 98/34094; WO 99/42810; WO 02/043486.
A significant problem with sex selected sperm cells may be that separation of sperm cells at rates sufficient to produce sex selected insemination samples or sex selected inseminates which are viable or sufficiently fertile for commercial application by conventional technology has necessitated increasing fluid stream pressure of flow cytometers or flow sort instruments to about 50 pounds per square inch. With respect to sperm cells of many species of mammals entrained in fluid streams having flow characteristics resulting from this application of pressure the viability, motility, or other fertility characteristics altered.
Another significant problem with sex selected sperm cell inseminates or sex selected sperm cell insemination samples can be the vast difference in sperm cell fertility characteristics which can vary greatly between samples. As such, success of artificial insemination performed under substantially identical conditions can result in correspondingly different pregnancy rates.
Another significant problem with existing sperm cell sex selection technology can be the lack of an assay from which fertility of sex selected sperm cells can be compared directly in-vivo (for example, in conjunction with artificial insemination procedures) and in-vitro (for example, in conjunction with IVF procedures).
The instant invention addresses the variety of problems associated with reduced sperm cell fertility spermatozoa that have been separated into enriched X-chromosome bearing and Y-chromosome bearing populations and the lack of heterospermatic assays to compare function and fertility of separated or sorted sperm cells, and in particular flow sorted sperm cells.